Because of the importance of integrated optics in the telecommunication industry, a great deal of effort has been expended to reduce insertion loss associated with coupling a light between integrated optical components, such as modulators and switches, and fiber links, to the lowest possible level and with reasonable expenses. Such components are generally known as multiplexers, modulators, couplers, switches and sensors. There is a particular need for improved optical modulation in some or all of these components and in the systems using them. This invention is an improvement on U.S. Pat. No. 5,060,307.
I have invented such components, which use a modified ordinary optical fiber. Wherein the fiber has a small area from which the cladding material has been removed and replaced with an active multilayer of materials structure, i.e. the modified cladding, which is sensitive to electromagnetic fields and should satisfy the conditions: in the presence of an external electromagnetic field, the optical properties of the active multilayer materials should change as well as the transmission characteristics of optical signals propagating within the modified region. The modified cladding is constructed of at least three layers; an inner metallic electrode coated directly on the core of the optical fiber, a layer of electrooptic material coated on the top of the first electrode, and a layer of a second electrode (outer electrode) covering the electrooptic material. Additional coating layers may be used between each two layers of the basic three layer structure to improve the interface properties. My device can be used as a modulator or switch. Also it can be used as an electromagnetic field sensor for determination of the applied external signal.
One important advantage of this invention is that it provides an optical modulation of the signal propagating within an optical fiber, which employs optical intensity, phase and/or polarization modulation by the continuous changing of the optical properties of the multilayer modified cladding resulting from external communication signals applied to the fiber modified region, e.g. RF or microwave signals, and can be used for the long distance transmission of these communication signals.
In addition, the device can be used as a high speed switch for switching off optical signals propagating in a communication link. The switching on-off is controlled by a high speed electric signal applied to the modified region of the fiber.
Other advantages will appear hereinafter.